1. Field of the Invention
The present invention relates to a water separation unit and a fuel supply apparatus for an internal-combustion engine.
2. Description of Related Art
Reduction in environment pollution caused by exhaust gas, and a response to resource depletion are formidable challenges to a current transportation system led by automobiles. Development of alternative fuel to conventional hydrocarbon fuel, and improvement of existing fuel such as gasoline and light oil are under consideration as alternative fuels to automotive fuel. For example, alcohol containing fuel, in which inexpensive alcohol is employed, draws attention. Alcohol fuel, in which only alcohol is used, and mixed fuel as a result of mixing alcohol into gasoline are known. Mixed fuel can be employed in an existing engine without modification, which is advantageous on the cost front.
However, there is a problem that water tends to be mixed into alcohol containing fuel. It seems that this water incorporation is caused because, alcohol itself has some amount of water, water is mixed in a process of mixing alcohol into gasoline before a tank truck is loaded with alcohol containing fuel, and water in the air is mixed into alcohol while an automobile is being refueled. In these cases, combustion failure is caused due to water, so that failures such as starting failure, power output decrease, and exhaust deterioration are caused. As well, corrosion in parts in a fuel system may be caused.
A conventional apparatus having a mechanism for draining water is disclosed in JP-U-54-97518. In the mechanism, water, which is separated and settled due to its density difference, is stored in the bottom of a fuel tank, and the stored water is drained by a drain syringe that is received inward of a cap of a refueling inlet. Also in JP-A-2001-179089, a method for separating and removing water is disclosed. According to the method, by using a material having adsorbability only for water and lacking an affinity for fuel as water adsorbent, water mixed into fuel is separated and removed.
However, when the apparatus in JP-U-54-97518 is applied to alcohol containing fuel, alcohol is included in the separated water because alcohol is soluble in water. Thus, alcohol as fuel is disposed of when water is drained, which is uneconomic. When the method in JP-A-2001-179089 is employed, the water adsorbent needs to be regularly replaced due to its capacity degradation, which takes man-hours. Furthermore, a filter for separating the water adsorbent from fuel is needed. Thus, a system for removing water becomes large-scale, which is inconvenient.